Digital technology has become pervasive in the creation and distribution of many types of media. Documents may be created and distributed in digital form both electronically and embodied in a carrier media such printed paper. Many valuable documents are produced and distributed in paper form that include printed images (possibly also including text) such as postal indicia and certificates of authenticity distributed with goods as part of a brand protection scheme.
Various technologies are now readily available for making high-quality copies of flat documents. Many image capture systems CCD cameras, CMOS sensors and scanners are readily available and that provide excellent reproduction accuracy and precision. Similarly, powerful digital media editing software and accurate and precise printing systems are readily available for outputting such unauthorized copies and counterfeit documents. As a result, unauthorized copying and counterfeiting of documents such as indicia, bank notes, checks, and identification documents is a serious concern. Accordingly, document creators and distributors must seek out more advanced technologies to thwart the efforts of such counterfeiters. Otherwise, members of society could not rely on the identity, authenticity and purported source of valuable documents.
Content owners may wish to provide identification, authentication and non-repudiation for certain printed images and/or documents including images. Several types of physical document copy detection systems are known including copy detection patterns (CDPs) that may be placed in a particular region of a document reserved for the purpose. Furthermore, several copy detection systems are known that utilize fragile watermarks, visible and invisible digital watermarks that are applied to an actual image or document. Commercially available systems include those available from Digimarc Corporation of Beaverton, Oreg. and Mediasec Technologies, LLC of Providence, R.I.
Copy detection systems that employ watermark or copy detection pattern (CDP) recovery must modify the target image. Accordingly, if the document owner does not wish to modify the original document, such techniques may not be used. Accordingly, there is a need for a copy detection system that does not require that the original image or document be modified. Additionally, there is an additional need for a copy detection system that is reasonably efficient.